Trained data transmission for communication systems

ABSTRACT

Various embodiments are described for a trained data transmission for communication systems.

BACKGROUND INFORMATION

Some communication systems may include features that may adapt to sometypes of changing conditions. For example, some systems allow a datatransmission rate to be adjusted based upon a detected transmissioncondition. A need exists for an improved technique to allow a system toselect or adapt a feature or parameter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a wireless communicationsystem in accordance with an embodiment of the invention.

FIG. 2 is a block diagram illustrating an example network according toan embodiment.

FIG. 3 is a flow chart illustrating operation of a system according toan example embodiment.

FIG. 4 is a diagram illustrating operation of a basic trained sequenceaccording to an example embodiment.

FIG. 5 is a diagram illustrating operation of a trained sequence thatuses a protection field according to an example embodiment.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the embodiments ofthe invention. It will be understood by those skilled in the art,however, that embodiments of the invention may be practiced withoutthese specific details. In other instances, well-known methods,procedures and techniques have not been described in detail so as not toobscure the foregoing embodiments.

Some portions of the detailed description that follows are presented interms of algorithms and symbolic representations of operations on databits or binary digital signals within a computer memory. Thesealgorithmic descriptions and representations may be the techniques usedby those skilled in the data processing arts to convey the substance oftheir work to others skilled in the art.

An algorithm is here, and generally, considered to be a self-consistentsequence of acts or operations leading to a desired result. Theseinclude physical manipulations of physical quantities. Usually, thoughnot necessarily, these quantities take the form of electrical ormagnetic signals capable of being stored, transferred, combined,compared, and otherwise manipulated. It has proven convenient at times,principally for reasons of common usage, to refer to these signals asbits, values, elements, symbols, characters, terms, numbers or the like.It should be understood, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as processing, computing, calculating,determining, or the like, refer to the action or processes of a computeror computing system, or similar electronic computing device, thatmanipulate or transform data represented as physical, such aselectronic, quantities within the registers or memories of the computingsystem into other data similarly represented as physical quantitieswithin the memories, registers or other such information storage,transmission or display devices of the computing system.

Embodiments of the present invention may include apparatuses forperforming the operations herein. This apparatus may be speciallyconstructed for the desired purposes, or it may comprise a generalpurpose computing device selectively activated or reconfigured by aprogram stored in the device. Such a program may be stored on a storagemedium, such as, but is not limited to, any type of disk includingfloppy disks, optical disks, CD-ROMs, magnetic-optical disks, read-onlymemories (ROMs), random access memories (RAMs), electricallyprogrammable read-only memories (EPROMs), electrically erasable andprogrammable read only memories (EEPROMs), flash memory, magnetic oroptical cards, or any other type of media suitable for storingelectronic instructions, and capable of being coupled to a system busfor a computing device.

The processes and displays presented herein are not inherently relatedto any particular computing device or other apparatus. Various generalpurpose systems may be used with programs in accordance with theteachings herein, or it may prove convenient to construct a morespecialized apparatus to perform the desired method. The desiredstructure for a variety of these systems will appear from thedescription below. In addition, embodiments of the present invention arenot described with reference to any particular programming language. Itwill be appreciated that a variety of programming languages may be usedto implement the teachings of the invention as described herein.

In the following description and claims, the terms coupled andconnected, along with their derivatives, may be used. In particularembodiments, connected may be used to indicate that two or more elementsare in direct physical or electrical contact with each other. Coupledmay mean that two or more elements are in direct physical or electricalcontact. However, coupled may also mean that two or more elements maynot be in direct contact with each other, but yet may still cooperate orinteract with each other.

It is worthy to note that any reference in the specification to “oneembodiment” or “an embodiment” means in this context that a particularfeature, structure, or characteristic described in connection with theembodiment may be included in at least one embodiment of the invention.The appearances of the phrase “in one embodiment” or “an embodiment” invarious places in the specification do not necessarily refer to the sameembodiment, but may be referring to different embodiments.

It should be understood that embodiments of the present invention may beused in a variety of applications. Although the present invention is notlimited in this respect, the circuits disclosed herein may be used inmany apparatuses such as in the transmitters and receivers of a radiosystem. Radio systems intended to be included within the scope of thepresent invention include, by way of example only, wireless local areanetworks (WLAN) devices and wireless wide area network (WWAN) devicesincluding wireless network interface devices and network interface cards(NICs), base stations, access points (APs), gateways, bridges, hubs,cellular radiotelephone communication systems, satellite communicationsystems, two-way radio communication systems, Time Division MultipleAccess (TDMA) systems, and the like, although the scope of the inventionis not limited in this respect.

As used herein, the term packet may include a unit of data that may berouted or transmitted between nodes or stations or across a network. Asused herein, the term packet may include frames, protocol data units orother units of data. A packet may include a group of bits, which mayinclude one or more address fields, control fields and data, forexample. Likewise, the term message may include any information, and mayinclude packets, frames, protocol data units or other units of data, orportions thereof.

Referring to the Figures in which like numerals indicate like elements,FIG. 1 is a diagram illustrating an example of a wireless communicationsystem in accordance with one embodiment of the invention. In thecommunications system 100 shown in FIG. 1, a user wireless system 116may include a wireless transceiver 110 coupled to an antenna 117 and toa processor 112. Processor 112 in one embodiment may comprise a singleprocessor, or alternatively may comprise a baseband processor and anapplications processor, although the scope of the invention is notlimited in this respect. According to one embodiment, processor 112 mayinclude a baseband processor and Medium Access Control (MAC).

Processor 112 may couple to a memory 114 which may include volatilememory such as DRAM, non-volatile memory such as flash memory, oralternatively may include other types of storage such as a hard diskdrive, although the scope of the invention is not limited in thisrespect. Some portion or all of memory 114 may be included on the sameintegrated circuit as processor 112, or alternatively some portion orall of memory 114 may be disposed on an integrated circuit or othermedium, for example a hard disk drive, that is external to theintegrated circuit of processor 112, although the scope of the inventionis not limited in this respect. According to one embodiment, softwaremay be provided in memory 114 to be executed by processor 112 to allowwireless system 116 to perform a variety of functions, which may includeone or more functions described below.

Wireless system 116 may communicate with an access point (AP) 128 (orother wireless system) via wireless communication link 134, where accesspoint 128 may include at least one antenna 118. Although not shown inFIG. 1, AP 128 may, for example, include a structure that is similar towireless system 116, including a wireless transceiver, a processor, amemory, and software provided in memory to allow AP 128 to perform avariety of functions. In an example embodiment, wireless system 116 andAP 128 may be considered to be stations in a wireless communicationsystem, such as a WLAN system.

Access point 128 may be coupled to network 130 so that wireless system116 may communicate with network 130, including devices coupled tonetwork 130, by communicating with access point 128 via wirelesscommunication link 134. Network 130 may include a public network such asa telephone network or the Internet, or alternatively network 130 mayinclude a private network such as an intranet, or a combination of apublic and a private network, although the scope of the invention is notlimited in this respect.

Communication between wireless system 116 and access point 128 may beimplemented via a wireless local area network (WLAN), for example anetwork which may be compliant with an Institute of Electrical andElectronics Engineers (IEEE) standard such as IEEE 802.11a, IEEE802.11b, IEEE 802.11g, IEEE 802.11n and so on, although the scope of theinvention is not limited in this respect. In addition, one or moreaspects of the invention in some cases may be considered to beextensions to one or more current standards.

In another embodiment, communication between wireless system 116 andaccess point 128 may be implemented via a cellular communication networkcompliant with a 3GPP standard, although the scope of the invention isnot limited in this respect.

Referring to FIG. 1, AP 128 may include a channel access control tocontrol access to one or more communication channels between AP 128 andone or more wireless systems. In one embodiment, the AP 128, through itschannel access control, may allow only one user (or one wireless system)to transmit data over a channel to the AP at a time. As examples, theremay be only one channel over communication link 134, or there may bemultiple channels over communication link 134 via use of frequencydivision multiplexing or other technique.

The wireless communication system of FIG. 1 may implement a technique tocontrol access to the channel or transmission medium or to selectivelygrant users a transmit opportunity (TXOP), for example. According to anembodiment, a TXOP may be a time period (or alternatively a maximumamount of data) during which a wireless system may initiate transmissionof data over the channel or transmission medium. This period of time forthe TXOP may be fixed for all TXOPs, or may be adaptively changed by theAP, for example.

According to an example embodiment, wireless systems may obtain accessto a transmission medium (e.g., obtain a TXOP) in a variety of differentways. According to one embodiment, a wireless system may obtain accessto a transmission medium, for example, by receiving a poll packet fromthe AP 128 or other station. Alternatively, the user wireless system 116may schedule one or more TXOPs in advance, such as by requesting TXOPsof a specified duration at requested times or at requested timeintervals (e.g., schedule 5 ms TXOP, every 100 ms).

In another example embodiment, a wireless system may use acontention-based access technique, such as Carrier SenseMulti-Access-Collision Avoidance (CSMA-CA), or other distributed accesstechnique to obtain access to the transmission medium. For example, astation may listen to (or sense) the medium. If the medium has been idlefor a minimum period of time, the station may begin transmitting. If themedium is busy, the station may, for example, wait until the medium isidle and then wait a random number of quiet time slots before beginningto transmit. These are just a few examples of how a wireless system mayobtain access to a transmission medium, although the invention is notlimited thereto. Wireless communication systems or networks may use avariety of different channel access techniques.

In addition, after obtaining access to the transmission medium, thestation may send a medium reservation message. For example, if themedium is quiet, the station may send a request to send (RTS) message.The AP (or other station) may reply with a clear to send (CTS) toconfirm that the medium has been reserved for transmission.

FIG. 2 is a block diagram illustrating an example network according toan embodiment. Network 200 may include one or more wireless stations,including, for example, station 1, station 2 and station 3. Each of thewireless stations in FIG. 2, including station 1, station 2 and station3, may be, for example, a user wireless system (such as system 116), anaccess point (AP) (such as AP 128), although the invention is notlimited to these types of stations. Stations 1-3 may be any type ofwireless station.

FIG. 3 is a flow chart illustrating operation of a network according toan example embodiment. At 305, station 1 (FIG. 2) may obtain access to atransmission medium. As noted above, a variety of different techniquesmay be used to obtain access to a channel or transmission medium, suchas polling, contention based access, etc.

At 310, station 1 may send (or transmit) a medium reservation requestmessage. According to an example embodiment, the medium reservationrequest message may include training information, although this is notrequired. According to an example embodiment, this medium reservationrequest message may be sent from station 1 to station 2 to perform twotasks: 1) to reserve the transmission medium (e.g., for a specifiedperiod of time); and 2) to initiate training. In an example embodiment,if training information is sent with the medium reservation message,such training information may be a known training sequence, although theinvention is not limited thereto.

In an example embodiment, the medium reservation request message may be,a Request to Send (RTS) message, or the like, which additionallyinitiates training, and may include training information, although theinvention is not limited thereto. This message may also include aduration field indicating the period of time for the requested mediumreservation, although the invention is not limited thereto. Thus, such amessage, which may both request a medium reservation and initiatetraining (and may also provide training information), is referred toherein as a Training Request To Send (TRTS) message.

At 315, station 2 may receive the TRTS message sent by station 1, whichmay include the training information. Station 2 may then measure atransmission condition. Various frequency bands or channels may receivevarious types of interference, noise, selective fading and otherconditions which may degrade the quality of a channel, from time totime. Station 2 may detect a transmission condition (e.g., as detectedby station 2), for example, of a particular frequency band or bands orchannel(s), for a particular transmission path, for each antenna, etc.,using a variety of different measurement techniques (e.g., using orbased upon the training information). For example, station 2 may measurea transmission condition by measuring a bit error rate (BER) or averageBER of the received signal (e.g., the received training sequence), bymeasuring a packet error rate or average packet error rate of thereceived signals, by measuring a signal to noise ratio (SNR) or averageSNR for received signals, by measuring a received signal strength, etc.,although the invention is not limited thereto. In another exampleembodiment, station 2 may measure a transmission condition based uponthe training information provided in the TRTS message. These are justexamples of how station 2 may measure the transmission condition, andmany other types of measurements may be performed.

At 315, in a multicarrier system, such as an OFDM (Orthogonal FrequencyDivision Multiplexing) system for example, where information may betransmitted over multiple carriers or subcarriers, station 2 may measurea transmission condition for each (or one or more) of the differentsubcarriers (e.g., per subcarrier), although the invention is notlimited thereto. A transmission condition may also be measured, forexample, on a per-antenna basis where multiple antennas are used, suchas received signal strength per antenna or SNR per antenna.

At 320, station 2 may transmit a medium reservation reply message tostation 1 that may include training feedback. Several different types oftraining feedback may be provided within the medium reservation replymessage. For example, the training feedback may include: 1) feedbackthat may describe the measured transmission condition(s) (e.g., themeasured SNR, BER, packet error rate, signal strength), which in someexample embodiments, may be provided on a per subcarrier basis, on a perantenna basis, etc.; and/or 2) feedback that may specify one or moretransmission parameters for station 1 to use in transmitting data tostation 2, although the invention is not limited thereto. In the lattercase (feedback actually specifying a transmission parameter(s)), station2 may measure a transmission condition, e.g., based on the trainingsequence, and then select one or more appropriate transmissionparameters based on the measured transmission condition(s), and thensend information identifying or specifying such transmission parametersto station 1 as training feedback within the medium reservation replymessage, at 320. These are just some examples, and other types oftraining feedback may be used.

The transmission parameters that may be selected or specified mayinclude, for example, transmission power, a code rate such as a FEC(forward error correction) code rate, decision to use interleaving (ortype of interleaving used), a modulation scheme(s) and/or data rate,etc., although the invention is not limited thereto. In one exampleembodiment, one or more of such transmission parameters may be selectedon a per-subcarrier basis, for example, transmission power persubcarrier, modulation scheme per subcarrier, coding rate persubcarrier, etc. Transmission parameters may also be selected on aper-antenna basis, where multiple antennas may be used at a transmitteror receiver.

In an example embodiment, the medium reservation reply message may be aClear to Send (CTS) message or the like, which in some exampleembodiments may also include a duration field indicating the period oftime for the requested medium reservation. In an example embodiment, theCTS message may also include the training feedback. Thus, in an exampleembodiment, the message sent by the station at 220 may be referred toherein as a Training Clear To Send (TCTS) message, although theinvention is not limited thereto.

At 325, station 1 receives the TCTS message from station 2. As notedabove, the TCTS message may include a field granting the requested mediareservation and may also include the training feedback. Station 1 maythen select (or adapt) one or more data transmission parameters based onthe received training feedback. The transmission parameters that may beselected or adjusted may include, for example, the FEC code rate,decision to use interleaving (or type of interleaving used), amodulation scheme(s) and/or data rate, etc., although the invention isnot limited thereto.

In an example embodiment, station 1 (and possibly other stations) mayinclude an adaptive modulator and may select one (or more) modulationschemes selected from a group of modulation schemes, based upon thetraining feedback. The modulation schemes may include, for example,binary phase shift keying (BPSK), quadrature phase shift keying (QPSK)(four different symbols to encode 2 bits/symbol), 8-PSK (8 differentsymbols to encode 3 bits/symbol), quadrature amplitude modulation (QAM),QAM 16 (16 different symbols to encode 4 bits/symbol), QAM 32, QAM 64,QAM 256, etc. For example, higher modulation schemes may preferably beused when better transmission conditions are present (e.g., lower biterror rate or higher SNR). These are just a few example modulationschemes and the invention is not limited thereto.

Referring to FIG. 3, at 330, station 1 may then transmit data to station2 or other station according to the one or more selected datatransmission parameters. For example, the data may be transmitted usingthe selected modulation scheme and the selected FEC code rate, which insome cases, may be selected on a per-subcarrier basis (e.g., for eachsubcarrier), a per channel basis, on a per antenna basis, etc.

FIG. 4 is a diagram illustrating operation of a basic trained sequenceaccording to an example embodiment. The sequence 400 illustrated in FIG.4 illustrates an exchange of messages between station 1 (STA1) andstation 2 (STA2) to allow station 1 to be trained (e.g., to select oradapt one or more transmission parameters based on training feedbackprovided by station 2) and then exchange data. The sequence may include,for example, two phases: a training phase 405 where station 1 andstation 2 may exchange messages to allow station 1 to be trained (e.g.,to allow station 1 to select or adapt one or more transmissionparameters); and a data phase 410 where data may be transmittedaccording to the selected transmission parameters.

In an example embodiment, the training phase 405 may begin wheneverstation 1 (STA1) gains access to the medium using whatever rules oraccess technique may be appropriate, such as through a polling accessmechanism or a contention-based access mechanism, etc., although theinvention is not limited thereto. Station 1 may then transmit a TRTSmessage 425 to station 2 (STA2). The TRTS message 425 may include amedium reservation request. The TRTS may be provided to request a mediumreservation and to initiate a training. The TRTS message 425 may alsoinclude training information. Station 2 may receive this TRTS message425 and then may measure a transmission condition. In an exampleembodiment, station 2 may measure the transmission condition based onthe training information provided in the TRTS message 425, although theinvention is not limited thereto. In addition, in an example embodiment,station 2 may also select one or more transmission parameters forstation 1 to use in transmitting to station 2, based on the measuredtransmission condition, although the invention is not limited thereto.

Station 2 may then transmit a TCTS message 440 back to station 1. TheTCTS message 440 may include a medium reservation reply, which may grantstation 1 its medium reservation request. The TCTS message 440 may alsoinclude training feedback, which may include, for example, informationdescribing a measured transmission condition or information actuallyspecifying one or more transmission parameters that station 1 maypreferably use for data transmission to station 2. This may complete thetraining phase 405.

The data phase 410 may then begin with station 1 transmitting one ormore data packets 430, 435, which may be transmitted according to theone or more transmission parameters selected based on the trainingfeedback. Station 2 may provide, for example, acknowledgements 445 and450 to data packets 430 and 435, respectively. In an example,embodiment, data packets 430 and 435 may each include multiple datapackets, and acknowledgements 445 and 450 may be selectiveacknowledgements to selectively acknowledge receipt of some of the datapackets.

In one example, embodiment, the TRTS message 425 may include a durationfield indicating a period of time for which the medium reservation isbeing requested. Likewise, the TCTS message 440 may also include aduration field to indicate the period of time for which the medium isbeing reserved for station 1. This duration field may be particularlyuseful where a third party station, such as station 3 (FIG. 2), may beunable to detect transmissions from station 1, but can detecttransmissions from station 2. Station 3 may receive the TCTS messagefrom station 2, including the duration field. Based upon receipt of theduration field in the TCTS, station 3 may preferably avoid transmittingor accessing the transmission medium through the data transmissionphase, although the invention is not limited thereto. Thus, in such acase, the duration field in the TCTS may be detected by station 3 andtherefore may decrease the likelihood of a collision between station 1and station 3 (as measured at station 2).

In an example embodiment, there may be two types of stations (ordevices), including legacy stations and non-legacy stations. A legacystation typically does not participate in the training process and maynot be able to demodulate or decode all fields or portions of TRTS andTCTS messages. A non-legacy station may participate in training and maygenerate and respond to TRTS and TCTS messages.

In an example embodiment, the TRTS and TCTS messages may be untrainedtype messages (e.g., packets), which may not have transmissionparameters for these messages selected or varied based upon training.Therefore, in an example embodiment, the untrained messages typically donot rely on a training process to vary or select their transmissionparameter(s). In an example embodiment, the data packets 430 and 435 maybe trained type messages since these packets may rely on a priortraining process and may be transmitted using one or more transmissionparameters selected or communicated by its intended receiver or selectedbased on a measured transmission condition.

The acknowledgements 445 and 450 may be, for example, either untrainedor trained type of messages.

In an alternative embodiment, the TRTS and the TCTS messages may be alegacy-compatible untrained type of message. In an example embodiment, alegacy-compatible untrained type of message may include a legacyportion, such as a valid legacy message, plus an additional trainingportion, although the invention is not limited thereto. The trainingportion of the legacy-compatible untrained type of message may include,for example, training information or training feedback. The trainingportion may be transmitted in the mixed type of message as one or moreadditional fields (e.g., in addition to the valid legacy message), byusing channels or subcarriers not used by the legacy device, or othertechnique. According to example embodiments, the training informationmay be a training sequence or other information to allow a station tomeasure a transmission condition, while training feedback may, forexample, describe a measured transmission condition(s) or may specifyone or more transmission parameters, although the invention is notlimited thereto. In another example embodiment, the TRTS message may bea mixed type of message, while the TCTS may be either a mixed or legacytype of message. A legacy type of message may be for example a messageused by legacy type stations. In an example embodiment, a legacy typemessage may typically be demodulated and decoded by legacy devices aswell as non-legacy devices that participate in training via TRTS andTCTS messages.

FIG. 5 is a diagram illustrating operation of a trained sequence thatuses a protection field. As noted above, the TRTS and TCTS messages mayinclude a duration field that may indicate the time period for themedium reservation. This duration field, in some cases, may protectagainst collisions caused by third party stations or hidden nodes. Theduration field in the TRTS and TCTS messages, for example, may informthe third party station to avoid transmitting over the medium until thereservation has ended.

Referring to FIG. 5, in some cases, a station may elect not to precede anew data phase with a training phase. For example, the station maydetermine that the previously selected transmission parameters can beused and thus, the overhead and delay associated with the training phasemay be omitted, although the invention is not limited thereto. In such acase, a station may precede a data phase 510 (or transmission of datapackets) with a protection portion 505. Station 2 may generate anacknowledgement 515.

The protection portion 505 may be information that indicates a mediumreservation for a period of time. This protection portion may include,for example, a duration field, or a portion of the legacy packet thatmay include a duration field, or a legacy packet that includes aduration field, although the invention is not limited thereto. Theduration portion (e.g., duration field) may inform other devices(including legacy devices) that the medium has been reserved for thespecified period of time, although the invention is not limited thereto.Therefore, in a case where a new data phase or new data packets arebeing transmitted without a corresponding training phase, a protectionportion (e.g., protection field or protection packet) may be transmittedprior to transmitting the data to assist in protecting this new dataphase against collisions from third party stations.

While certain features of the embodiments of the invention have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the embodiments of the invention.

1. A method of transmitting information between first and secondwireless stations, the method comprising: performing a training phaseincluding an exchange of medium reservation messages between the firstand second stations to reserve a medium and to select at least one datatransmission parameter, at least one of the medium reservation messagesincluding a duration field indicating a duration of the mediumreservation; performing a first data phase including sending data fromthe first station to the second station according to the transmissionparameter selected during the training phase, wherein the selectedtransmission parameter is selected on a per-antenna basis, wheremultiple antennas are used at said the second station; performing asecond data phase without first repeating the training phase, the seconddata phase comprising: transmitting a protection portion from a firststation to the second station, the protection portion including aduration field indicating the duration of the reserved medium; andtransmitting data from the first station to a second station accordingto the at least one transmission parameter.
 2. The method of claim 1,the exchange of medium reservation messages in the training phasecomprising: receiving a medium reservation request message at the secondstation to initiate training and to request a medium reservation, saidmedium reservation request message includes training informationcomprising a training sequence; and sending a medium reservation replymessage from the second station granting a medium reservation requestand providing training feedback describing at least one measuredtransmission condition.
 3. The method of claim 2, the at least onemeasured transmission condition measured on a per antenna basis usingeach antenna where multiple antenna are used at the second station. 4.The method of claim 2 wherein the feedback describing at least onemeasured transmission condition comprises at least one from the groupcomprising: a measured signal to noise ratio; a presence of errors ornot in received training information or other information; a number oferrors detected; a bit error rate or packet error rate; or a measuredsignal strength.
 5. The method of claim 4 wherein the measuredtransmission condition is measured on a per subcarrier basis.
 6. Themethod of claim 1 wherein the selecting at least one data transmissionparameter comprises selecting a data transmission parameter from thegroup including: a data rate; a modulation scheme; a coding rate; use ortype of interleaving; and transmission power.
 7. The method of claim 6wherein the selected data transmission parameter is selected on a persubcarrier basis.
 8. A method comprising: selecting at least one datatransmission parameter; transmitting a protection portion from a firststation to a second station, the protection portion including a durationfield indicating a duration of a reserved medium; and transmitting datafrom the first station to the second station according to the at leastone selected transmission parameter, wherein the selected transmissionparameter is selected on a per-antenna basis, where multiple antennasare used at said the second station.
 9. The method of claim 8, the atleast one data transmission parameter selected according to an exchangeof messages in a training phase, the exchange of messages comprising:receiving a medium reservation request message at the second station toinitiate training and to request a medium reservation, said mediumreservation request message includes training information comprising atraining sequence; and sending a medium reservation reply message fromthe second station granting a medium reservation request and providingtraining feedback describing at least one measured transmissioncondition.
 10. The method of claim 9, the at least one measuredtransmission condition measured on a per antenna basis using eachantenna where multiple antenna are used at the second station.
 11. Themethod of claim 9 wherein the feedback describing at least one measuredtransmission condition comprises at least one from the group comprising:a measured signal to noise ratio; a presence of errors or not inreceived training information or other information; a number of errorsdetected; a bit error rate or packet error rate; or a measured signalstrength.
 12. The method of claim 11 wherein the measured transmissioncondition is measured on a per subcarrier basis.
 13. The method of claim8 wherein the selecting at least one data transmission parametercomprises selecting a data transmission parameter from the groupincluding a data rate; a modulation scheme; a coding rate; use or typeof interleaving; and transmission power.
 14. The method of claim 13wherein the selected data transmission parameter is selected on a persubcarrier basis.
 15. The method of claim 8, further comprisingobtaining access to a wireless transmission medium prior to transmittinga medium reservation request message.
 16. The method of claim 1, whereinthe duration field comprises at least one of: a legacy packet thatincludes a duration field, or a portion of a legacy packet that includesa duration field.
 17. The method of claim 8, wherein the duration fieldcomprises at least one of: a legacy packet that includes a durationfield, or a portion of a legacy packet that includes a duration field.18. A method of transmitting information between first and secondwireless stations, the method comprising: performing a training phaseincluding an exchange of medium reservation messages between the firstand second stations to reserve a medium and to select at least one datatransmission parameter, at least one of the medium reservation messagesincluding a duration field indicating a duration of the mediumreservation; performing a first data phase including sending data fromthe first station to the second station according to the at least onedata transmission parameter selected during the training phase, whereinthe selected transmission parameter is selected on a per-antenna basis,where multiple antennas are used at said the second station; performinga second data phase without first repeating the training phase, thesecond data phase comprising transmitting data from the first station toa second station according to the at least one data transmissionparameter.
 19. The method of claim 18, wherein the training phasecomprises the second station indicating the at least one datatransmission parameter to the first station.
 20. The method of claim 18,wherein indicating the at least one transmission parameter comprisesindicating a modulation scheme and a forward error correction (FEC)coding rate.